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EPR studies of wild-type and several mutants of cytochrome c oxidase from Rhodobacter sphaeroides: Glu286 is not a bridging ligand in the cytochrome a3-CuB center.

Authors
  • Mitchell, D M
  • Aasa, R
  • Adelroth, P
  • Brzezinski, P
  • Gennis, R B
  • Malmström, B G
Type
Published Article
Journal
FEBS Letters
Publisher
Wiley (John Wiley & Sons)
Publication Date
Nov 06, 1995
Volume
374
Issue
3
Pages
371–374
Identifiers
PMID: 7589573
Source
Medline
License
Unknown

Abstract

Wild-type and several mutants of cytochrome c oxidase from Rhodobacter sphaeroides were characterized by EPR spectroscopy. A pH-induced g12 signal, seen previously in mammalian cytochrome oxidase and assigned to the presence of a bridging carboxyl ligand in the bimetallic cytochrome a3-CuB site, is found also in the bacterial enzyme. Mutation of glutamate-286 to glutamine inactivates the enzyme but does not affect this signal, demonstrating that the carboxyl group of this residue is not the bridging ligand. Three mutants, M106Q, located one helix turn below a histidine ligand to cytochrome a, and T352A as well as F391Q, located close to the bimetallic center, are shown to affect dramatically the low-spin heme signal of cytochrome a. These mutants are essentially inactive, suggesting that these three mutations result in alterations to cytochrome a that render the oxidase non-functional.

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